The present invention relates to a method in the tail threading of a web-forming machine, in which a threading tail is formed from the web, and is transferred to the production section of a web-forming machine including a draw point, and in which method monitoring takes place of both the formation of the threading tail and its transfer to the draw point, which is at the start of the said production section, and from which the threading tail is pulled in the tail threading towards a holding point at the end of the production section. The invention also relates to a corresponding arrangement in the tail threading of a web-forming machine.
European patent application number 1335067 discloses a method and arrangement in transferring the web from one production section of a paper machine to another. In the tail threading, a threading tail, which is cut from the web, is used in the tail threading. According to the application, the forming of the threading tail is monitored, for example, using camera. If something abnormal occurs in the threading tail or in the path of its travel, the formation of the threading tail, or its transfer to the next production section, are adjusted using the control system. For example, on the basis of a detected deviation, water cutting can be adjusted, either manually, or automatically.
The arrangement is intended for monitoring and controlling the formation of a threading tail between production sections. The camera can also be used to determine the failure of the tail threading of the threading tail to the roll nip, forming the draw point in the following production section. Problems arising after the point in question will, however, remain unnoticed. In addition, the automatic control disclosed is usually impossible, if formation of the threading tail fails completely. This is because, at present production speeds, only a moment is needed for commencing tail threading. If tail threading fails immediately when it starts, it will thus be impossible to use software to control its formation. In other words, the method and apparatus disclosed can only be used to monitor one part of the tail threading. Despite the numerous adjustment possibilities, adjustment is often also impossible in practice, as tail threading takes a maximum of a few seconds. In addition, monitoring both before and during tail threading leads to long imaging times, which require an accurate camera and powerful peripheral devices. Despite the versatile equipment, it is impossible to use the arrangement to determine whether the tail threading has succeeded, never mind determining the problem points that caused it to fail.